For the first time in its six-year history, the premium denim label is moving beyond jeans to offer 140 sportswear pieces beginning next spring. With retail prices running between $200 and $1,500, J Brand is aiming to sell its new collection alongside Helmut Lang, Rag & Bone, Isabel Marant and Carven on the retail floor.

“The initiative we set out from the very beginning was to build a fashion brand,” said J Brand chief executive officer Jeff Rudes. “We don’t want to put ourselves out there as [just] a jean brand.”

A look around Rudes’ office in a gritty part of Los Angeles revealed that J Brand is moving in that direction. Blown-up photos from ad campaigns showed model Lily Aldridge crouching in jodhpur-style jeans and a fur vest or standing proudly in velvet jeans and a matching tuxedo blazer. The company already has flirted with high-end fashion through denim collaborations with Hussein Chalayan and Proenza Schouler.

Waiting until 2012 to introduce the new line — well after rivals such as Seven For All Mankind, Joe’s Jeans and True Religion have churned out several sportswear collections — allowed J Brand to build a significant denim business at retailers such as Barneys Co-op, Harvey Nichols, Ron Herman, Net-a-porter.com, Montaigne Market and Bloomingdale’s.

“It was all about timing — the distribution, the growth of the brand, the brand recognition in the marketplace,” Rudes said. “So when we did launch ready-to-wear, our customer base was ready for it.”

Arnie Gale, J Brand’s president of sales, said that only 60 of its 2,500 current retail doors will carry the line in the first season. Retailers will get a peek at the collection on Sept. 7, when J Brand will hold sales meetings in the Meatpacking District around the start of New York Fashion Week. Afterward, the company will meet with buyers in London, Milan and Paris.

Rudes expects the initiative to contribute less than 10 percent of total sales in its first year. With about 190 employees, J Brand projects company sales will exceed $100 million this year.

J Brand has goals beyond sportswear. Rudes aims to open a flagship in London or New York within the next three years. In five years, he plans to be operating a store in every fashion capital. “L.A., Paris, Milan, Tokyo — beyond that we’ll see,” he said.

The company’s aspirations were helped last year when Star Avenue Capital LLC acquired a majority stake in J Brand in a deal said to be worth more than $50 million. It was the first major investment for Star Avenue, which is a three-way partnership involving unlikely associates — Star’s management, Irving Place Capital and Creative Artists Agency.

While the sportswear effort will be the focus for 2012, J Brand is eyeing more product extensions, such as shoes and handbags, in 2013. A men’s sportswear component is already being discussed to launch within the next 18 months.

Although Rudes decided not to give the new collection a different name, he set up a staff that handles sourcing, patternmaking, design and sales separately from the denim division. Spearheading J Brand’s sportswear launch is Donald Oliver, a Scotsman who joined the company six months ago as design director for the new collection after stints at DKNY Jeans, Vera Wang, Gap Inc. and Calvin Klein.

In describing J Brand’s sportswear customer, Oliver said, “From Day One, we wanted her to be easygoing, uncomplicated, subtly sophisticated. We wanted her to feel relevant, not trendy, not like she’s trying too hard, which is why I think the garments have an ease about them.”

J Brand’s debut sportswear collection is clean, minimal and full of unexpected details. The palette is muted in black, white, lilac, heather gray, sky blue and peach. With the exception of some striped linings, prints are absent.

Despite his knowledge of denim, Oliver limited the use of the rugged fabric to the selvage taping sewn on the epaulets of cotton-silk chambray shirts. Instead, he preferred unusual but rarefied fabrics, such as garment-dyed Cupro and cotton blended with Japanese paper. He also applied treatments that J Brand uses regularly on jeans to nondenim fabrics. For example, he crafted wax-coated cotton twill into trousers with an elastic waistband.

Intended to complement denim, several of the jackets and tops could be tossed nonchalantly over jeans. There’s a cropped khaki mackintosh coat cinched at the waist with gray cotton taping, as well as a hand-knit bolero sweater.

“We paid a lot of attention to details, making the garment feel special to the wearer,” Oliver said, pointing to the pin-striped acetate lining and slate blue polished silk panel sewn inside a gray linen blazer and contrasted with black leather trim along the edges of the lapel and front hem.

The collection also provides something if a woman can’t wear denim — for instance, at a corporate office. High-twist cotton twill forms the base for matching flat-front trousers, chinos, shorts and a blazer.

“It’s important that we looked at her as a whole,” Oliver said. “We just didn’t want to look at her as working or going out. It’s about building an aspirational wardrobe for our girl.”